1. Field of the Invention
The present invention relates to a welding robot, and in particular to a process for detecting an initial welding point of the welding robot.
2. Description of the Related Art
In welding operations in an automated production line, due to the irregularity and/or displacement of an object to be welded, it is very difficult to precisely detect the initial welding point, even though the welding robot constantly moves along a predetermined path. This is due to the fact that although the positions of welding robots are always constantly maintained by fixing jigs and frames in automated production lines of factories, it is very difficult to precisely position objects to be welded within assigned working spaces on a conveyor or a positioner carrying those objects. Furthermore, certain objects can deviate from size standards, although the deviation may be minute.
In order to solve these problems, a process for detecting the initial welding point through touch sensor tracking has been developed. Touch sensor tracking is a process for precisely finding the position of an object by identifying whether electric current flows between a welding wire or nozzle and the object, while the welding arc is not produced and prior to practical welding. Though the parent metal and the welding wire are ordinarily separated from each other, the initial welding point can be detected by recognizing the point where the two parts become short-circuited, while the welding torch is gradually moved.
Examples of commercially available systems developed using the above principal are FANAC, DAIDEN, ABB, and IGMC. In these systems, a drive source for the touch sensor is mounted outside, so that the touch sensor touches four or five reference points for precise positioning even when the parent metal is either tilted or inverted.
More precise positioning can be accomplished through more touch times. However, as the touching cycles are increased, the touching period is increased, and thus the reduction of the required welding time, which is a very serious factor in mass welding process, is adversely affected.